Single command acoustical guidance system

ABSTRACT

1. A method of destroying a target with a homing torpedo comprising the steps of detecting the target range and bearing in a passive manner, computing the expected target position after a predetermined period of time from the initially detected range and bearing, adjusting a torpedo turning means mounted on the torpedo prior to the launching of the torpedo to cause the torpedo to turn through a fixed angle upon actuation by a signal, launching the torpedo toward the expected target position, rotating a disc having indicia at a position remote from the torpedo, rotating a disc on the torpedo in synchronism with the indicia bearing disc, generating an acoustic signal only when the torpedo is approximately a predetermined distance from the target to actuate the turning means, the direction of the torpedo being controlled by the position of the disc on the torpedo, generating the acoustic signal exactly at a time indicated by the indicia bearing disc corresponding to the direction of the target relative to the torpedo, whereby the torpedo is directed to an area where it can home on the target.

United States Patent 11 1 Ellingson et al.

1 1 June 24, 1975 1 SINGLE COMMAND ACOUSTICAL GUIDANCE SYSTEM [75] Inventors: Herman E. Ellingson, Silver Springs,

Md.; Gilbert Lieberman, Haddonfield, NJ.

[731 Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

221 Filed: 11:11.2, 1961 211' App], No.5 86,825

[52] US. Cl 114/20 R [51] Int. Cl. F42B 19/00 [581 Fieldofsearch ll4/2l,2l W,Zl.l,20, 1 14/23 [56] References Cited UNITED STATES PATENTS 913,372 2/1909 Gardner 114/21 1,301,690 4/1919 Hammond 114/21 W 1.418,?88 6/1922 Hammond 114/21 W 1,553,650 9/1925 'lrcnor 1 114/21 2,305,485 12/1942 Merriam 114/21 W 2,397,088 3/1946 Clay 244/14 RUDDER CONTROL POWER SOURCE Primary Examiner-Samuel Feinberg Attorney, Agent, or Firm-R. S. Sciascia; J. A. Cooke EXEMPLARY CLAIM 1. A method of destroying a target with a homing torpedo comprising the steps of detecting the target range and bearing in a passive manner, computing the expected target position after a predetermined period of time from the initially detected range and bearing, adjusting a torpedo turning means mounted on the torpedo prior to the launching of the torpedo to cause the torpedo to turn through a fixed angle upon actua tion by a signal, launching the torpedo toward the expected target position, rotating a disc having indicia at a position remote from the torpedo, rotating a disc on the torpedo in synchronism with the indicia bearing disc, generating an acoustic signal only when the torpedo is approximately a predetermined distance from the target to actuate the turning means, the direction of the torpedo being controlled by the position of the disc on the torpedo, generating the acoustic signal exactly at a time indicated by the indicia bearing disc corresponding to the direction of the target relative to the torpedo, whereby the torpedo is directed to an area where it can home on the target.

9 Claims, 7 Drawing Figures PATENTEDJUN24 1915 3,890,913

SHEET 1 F I (1.1. U I 2,000 4,000 6,000 8,000 lqfw vos.

F 16.2. if I ,000 .000 I .000 8,000 I 10,000

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37-; I RUDDER CONTROL POWER f SOURCE I33 37 I43 H '1 I44 42 INVENTORS, TRANSMITTER g ATTYS.

SINGLE COMMAND ACOUSTICAL GUIDANCE SYSTEM The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to torpedoes and more particularly to a method and system for directing a torpedo toward a target.

Previously, submarine torpedoes were directed toward targets by continuously sending signals from the submarine to the launched torpedoes and these signals were used to continuously guide the weapon through the water toward the appropriate target. The continuous communication was achieved either by continuously emitting acoustic signals or by using a wire guided" torpedo system. With the acoustic type of apparatus previously employed it was necessary to continuously determine the position of both the torpedo and the target. This resulted in a highly complex system which frequently resulted in errors by the shipboard personnel in correctly steering the torpedo toward the target.

The prior art acoustic system depended greatly on oceanographic communication conditions between the torpedo and the launching submarine. If the conditions were not proper, the signals transmitted from the submarine frequently would not reach the torpedo and it would be misguided, resulting in a miss of the target. In addition, continuous communication between the torpedo and the launching submarine made detection by the enemy target easily accomplished. When the launching submarine and the torpedo location were ascertained by the enemy, the enemy was able to make evasive maneuvers thus avoiding the torpedo, and at the same time could launch a counterattack against the launching submarine. Thus, the submarine effectiveness was virtually destroyed and it was made vulnerable toenemy attack. Also, when continuous communication between the submarine and the torpedo is maintained passive detection of the target will become virtually impossible because of all the strong signal sources generated between the launching submarine and the torpedo will tend to null out the target signals.

Wire guided torpedoes have not proved feasible because of the great amount of wire which must be used to guide them particularly to great distances, i.e., I0,000 yards.

Accordingly, it is an object of this invention to provide a new and improved torpedo and torpedo guidance system and method which does not require continuous guidance after a torpedo has been launched from a submarine; in which it is not necessary to continuously determine both target and torpedo positions; and which is not dependent on oceanographic conditions to any great extent for accurately guiding the tor pedo to the target.

Other objects of this invention are to provide a torpedo guidance system and method in which the enemy vessel will become unable to detect the launching submarine or the torpedo until it is too late for it to destroy either the submarine or to evade the torpedo; and in which passive detection of the enemy target can easily be accomplished by the launching submarine without interference from torpedo signals after a torpedo has been launched.

Additional objects of this invention are to provide a torpedo having a guidance system built thereon which turns the torpedo through a predetermined angle when a remotely located signal is generated; the signal determining the direction in which the turn will be made.

Other objects of this invention are to provide a new and improved torpedo guidance system and method that is simple, inexpensive, and easily adapted to existing equipment.

Various other objects and advantages will appear from the following description of several embodiments of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

The manner in which this invention achieves these objects can best be understood by reference to the accompanying drawings in which:

FIG. 1 is a schematic illustration of one mode by which this invention may be carried out wherein the torpedo turns FIG. 2 is another schematic illustration of a mode by which this invention may be carried out wherein the torpedo turns 45;

FIG. 3 is an illustration ofa torpedo partly in section, illustrating its control elements in accordance with this invention;

FIG. 4 is a schematic diagram ofa submarine and the apparatus used thereon to transmit the signals to the torpedo;

FIG. 5 is one embodiment of a torpedo guidance control element in accordance with this invention;

FIG. 6 is an illustration of a disc which might be carried on a launching submarine for directing the guidance mechanism of FIG. 5 in the correct direction to ward the enemy vessel; and

FIG. 7 is a schematic diagram of another embodiment of a torpedo guidance control element in accordance with this invention.

Of course, it is to be understood that like reference characters designate like or similar parts throughout the several views of the drawings.

Referring now to FIG. 1 of the drawings which is a schematic representation of one method by which the submarine 11 can destroy the vessel 12, usually another submarine, in accordance with this invention. Submarine 11 can ascertain the presence and location of ship 12 by conventional sonar apparatus, preferably of the passive type, such as disclosed in the application of John C. Munson, Ser. No. 802,575 for Passive Underwater Target Detection and Locating System, filed on Feb. 27, 1959, and of common assignee as this application. After the movements of submarine 12 have been observed by the personnel manning the detection equipment aboard ship 11 for a short period of time, the predicted course of the target 12 may easily be calculated. In the example shown of FIG. 1 of the drawings, it is determined that ship 12 will move from the location where it is shown on the figure to the point 13 by way of a straight line 14 if it remains on its previously ascertained course. In this example it is assumed that the target is approximately 10,000 yards away from the submarine II and it has a speed of approximately 10 knots while the speed of a torpedo that will be launched from submarine 11 is between 27 and 30 knots, thus the torpedo will travel approximately three times as far as the target I2 in a like period of time. Under these conditions, torpedo 15 is launched from submarine 11 along a straight line path 16 toward point 13, the torpedo running time being about minutes between submarine l1 and point 13.

Let it be assumed that the enemy submarine l2 deviates from its predicted course along line 14 immediately after the torpedo is launched from submarine l l, by making a 40 turn toward the launching submarine, and that ship 12 now begins to travel the course depicted along line 17. The resulting change in target course is observed by the detecting equipment contained on submarine 11. With passive detection equipment. such as disclosed in the previously mentioned application of Munson, it is possible to accurately determine target range and bearing at any time during the torpedo run. Since the torpedo course is a predetermined straight line, its position is always known on board the launching submarine 11. Accordingly, it is possible to turn torpedo 15 90 in a direction toward the target when the torpedo is a minimum distance from the target by use of a single signal generated remotely from the torpedo, preferably on board submarine 11. In most situations, with torpedo-to-target speed ratios of three to one, the torpedo will be located within 1,900 yards of the target after the turn has been executed. When the turn command is given, the enemy vessel 12 will be located at point 18 and will be unable to employ evasive tactics sufficiently to take it out of the torpedos lethal area. The target 12 will be able to maneuver in an area of approximately 600 yards as shown by the area 19 while the torpedo is making its turn and moving to the point 21. Since the torpedo 15 is of the homing type, having a lethal or homing range of approximately 800 yards, the enemy ship 12 is within the torpedos homing range. Thus, the target is unable to avoid the torpedo after it has made a right angle turn at point 22 and the torpedo is guided to the target by a single signal.

Referring now to FIG. 2 of the drawings, illustrating a second mode of operation of this invention, wherein target 12 is approaching submarine 11 from a head-on position, located 10,000 yards away. In this situation it will be assumed that the range information is not as accurate as it was in the situation considered in FIG. 1, accordingly the torpedo will make a 45 turn rather than a 90 turn because of the greater error which might be encountered. Immediately after the torpedo 15 is launched from submarine 11, enemy ship 12 deviates from its previous course by making a 40 turn along line 26. When the torpedo gets approximately 7,000 yards away from the submarine 11, its course is altered by a single signal generated on board the launching submarine directing it to make a 45 turn toward enemy submarine 12. The escape area 19 for submarine 12 is increased when the angle of turn is decreased from the maximum 90 turn because the distance the torpedo must travel before reaching the le thal area is increased. However, for the most practical purposes, the escape area is not so large as to render this mode of operation useless. The point 22 where the torpedo 15 should be turned can easily be calculated by using standard trigometric and algebraic equations, depending upon the detected information and the predetermined angle of turn.

Referring now to FIG. 3 of the drawings, a schematic representation of the aft portion of the torpedo control section, wherein electric acoustic detector 31, rudder control element 132 and power source 133 are schematically shown in the partial sectional view of the torpedo 1S. Detector 31 receives a compressional wave signal generated by submarine II and couples the detected signal to rudder control element 132 which is supplied by power from source 133 by suitable means,

shown on the drawings as pipes. Power source 133 also drives propellers [34 mounted in the rear section of the torpedo. The torpedo is maintained in a stable nonrotating position in the water by means of vertical and horizontal fins I35 and 136. Vertical rudder 37 controlled by rudder control means 132 turns the longitudinal torpedo axis through the predetermined angle which it is to be turned.

Referring now to FIG. 4 of the drawings, there is disclosed a submarine and the apparatus used thereon to direct the torpedo to make the desired turn in the correct direction at the correct time. In one embodiment of the invention, a transmitter 141 is coupled to electroacoustic transducer 142 causing suitable pressure waves of predetermined frequencies to be generated through the water upon actuation of a command signal. Transmitter 141 contains an oscillator or a pair ofoscillators for generating signals of frequenciesf andf at separate times, the frequency f preferably being approximately 5,000 cyclcs per second and the frequency ji being 2,000 cycles per second. In another embodiment of the invention a small explosive 143, on the order of one-eighth of a pound, may be mounted on the conning tower 144 of the submarine and will be actuated upon the reception of a suitable command signal from the submarine.

Referring now to FIG. 5 of the drawings, there is illustrated one embodiment of the control apparatus contained in the torpedo for controlling its movement through the water. The electroacoustic transducer 31 mounted on the outer torpedo shell is coupled to amplifier 32 and bandpass filter 33 which eliminates spurious noises that might be generated in the sea. The output of bandpass filter 33 is coupled to the input coils of relay 34 having a plurality of output armatures 35, 36 and 30, armatures 35 and 36 being normally open and armature 30 being normally closed. Armature 30 normally couples power supply 38 to synchronous motor 39 which drives shaft 41 at a slow rate of speed, such as one rotation every 24 seconds. Disc 42 is continuously driven by the motor and has an insulated portion 43 and a conducting portion 44 which is always connected to ground terminal 45. Stationary brushes 46 and 47 are coupled to the disc 42 and transmit any electrical current through the brushes to the terminals 48 and 49, respectively, of the normally open relay contacts. Relay armatures 35 and 36 are respectively coupled to voltage sources 51 and 52 of opposite polarities. Potentiometers 53 and 54 are connected respectively across each of the voltage sources 51 and 52 and have their respective sliders driven by ganged shafts 56 and 57, ultimately controlled by knob 55. The slider position determines the magnitude of the voltage fed into gyro compass 58 having a grounded input terminal which voltage may for example cause a rotational shift in the gyro housing which may be detected by a suitable pick off device to produce an electrical signal indicative of the rotational shift of the gyro housing. The output of gyro compass 58 is supplied to motor 59 which drives rudders 37 through gear train 61 so that rudders 37 are both turned in the same direction. If positive voltage source 51 is fed to gyro compass 58 when the relay is actuated. the rudders 37 will be rotated so that the longitudinal torpedo axis will effect a turn in the left direction, but if negative voltage source 52 is supplied to the gyro compass, the torpedo will turn toward the right.

A disc 65, shown on FIG. 6, driven by a motor contained on hoard submarine I1 is synchronized with the rotation of motor 39 contained on the torpedo 15. When the disc 65 is rotated so that segment 66 is in proximity to pointer 71, a command signal is generated by exploding charge 143 so that the torpedo will be rotated to the left, while the torpedo is rotated to the right when the segment 67 is in proximity to pointer 71. Each quadrant of the disc is arranged so as to represent approximately 10,000 yards of acoustic pulse travel time through the water medium through' which the torpedo is traveling. The time required for the acoustic signal to travel from the submarine to the torpedo will vary with the distance of the torpedo from the submarinc and therefore, the provision of sectors 68 and 69 upon disc 65 assures the operator that the torpedo will be turned in the direction intended when the signal is received. Stated in another manner, if disc 65 were provided with only two sectors, the time lag caused by the travel time of the acoustic signal from the submarine to the torpedo will cause the torpedo to turn in the opposite direction than that intended if the acoustic signal was initiated at a point of time when one of the sectors was just about to come into registry with the reference point 71. When either sector 68 or 69 is in the proxim ity to pointer 71, no command is to be given as this is a time in which incorrect direction of turn information may reach the torpedo and the disc 42 rotated by motor 39 (FIG. 5) may not be in position corresponding to the desired left or right hand turn. It is to be understood that the disc 65 may be color coded so that each of the segments 66 and 67 appears as different colors, e.g. red for segment 66 and blue for segment 67 while the segments 68 and 69 correspond to a neutral or white color.

The operation of the embodiments disclosed in FIGS. 5 and 6 will now be described in detail. An operator on board the launching submarine 11 observes the new course of enemy vehicle 12 (FIGS. 1 or 2) and determines the range and bearing thereof in accordance with the apparatus as disclosed in the previously mentioned application of Munson. Since the torpedo 15 is launched with constant speed on a know course, i.e., a straight line, its position is always known by the operator. Accordingly, the operator knows when the torpedo is at point 22, the point on line 16 where the torpedo is a minimum distance away from the target. In the embodiment disclosed in FIG. 1 it is desired to turn the torpedo toward the left. Thus with the disc 65 in the position shown in FIG. 6, the operator will immediately actuate one of the explosive sources 143, FIG. 4, mounted on the submarine conning tower. If either of the segments 67, 68 or 69 is in front of pointer 71, the operator must wait until the disc is rotated by a motor synchronized with the motor on the torpedo so that quadrant 66 is in proximity to the pointer. During the maximum period of time which it may take for the segment 66 to appear next to pointer 71, e.g. 18 seconds if the disc rotates once every 24 seconds. the torpedo will travel approximately 250 yards through the water. This distance will not adversely affect to any great extent the kill probability ofwhich the torpedo is capable.

The explosive signal is communicated through the water medium and is detected by electroacoustic receiver 31 contained on the torpedo approximately 6 seconds after it is generated. When the signal is detected and fed through amplifier 32 it actuates relay 34 which causes armatures 35 and 36 to come into contact with terminals 48 and 49, respectively, Wl'lllL simultaneously causing armature 30 to open. The opening of armature 30 removes supply 38 from the control winding of motor 39 causing this motor to stop, disc 42 assuming the position in which it was located when the signal was detected by transducer 31. When the relay 34 is actuated, a circuit is established from ground 45 through the conducting portion 44 of disc 42, through either armature 35 or 36 and potentiometer 53 or 54 to gyrocompass 58.'

If it is assumed that brush 46 engages the conducting segment 44 of the rotating disc (as shown in the drawing) a positive voltage is supplied to the input of the gyrocompass. The slider position of potentiometer 53 determines the angle through which the motor 59 will drive the rudders 37 initially. In this embodiment it will be assumed that the longitudinal torpedo axis is to be turned in a left direction and that this is accomplished by means of a positive voltage supplied to the gyrocompass. If the explosive signal was generated at a time when the quadrant 67 of disc 65 contained on the launching vessel was in proximity to the pointer 71, a right turn would be effected by the torpedo and a circuit would be established to the gyrocompass through potentiometer 54, armature 36, brush 47 and conduct ing portion 44 of disc 42 to ground. The gyrocompass 58 produces a signal which causes motor 59 to turn the rudders 37 through gears 61 until the torpedo assumes the direction in which it was directed to turn. The angle of turn in either direction is controlled by the variable setting of the potentiometer slider position.

Referring now to FIG. 7 of the drawings in which still another embodiment of the steering apparatus contained on board the torpedo is disclosed. If the torpedoes are to be equipped with this apparatus, it is necessary for the launching submarine to contain a transmitter capable of emitting a pair of dissimilar frequency signals through the water as shown by the transmitter 141 of FIG. 4. Only a single frequency signal is to be generated at the proper time. When the torpedo 15 reaches the turning point 22 shown in FIGS. 1 or 2, a signal of predetermined frequency is generated by transmitter 141 and coupled to electroacoustic transducer 142 on board the submarine. If it is desired that the torpedo 15 make a left turn. as shown on FIG. 1, a signal of frequency f preferably approximately 2,000 cycles per second is generated; if it is desired to have the torpedo make a right turn, as shown on FIG. 2, a signal of frequency f which is preferably approximately 5,000 cycles per second is produced from the transmitter 141 and received by detector 31 on board the torpedo.

The signal detected by transducer 31, FIG. 7, is coupled through amplifier 32 to a pair of bandpass filters 73 and 74. Filters 73 and 74 will only pass signals in the frequency bands associated with the signals f, and f generated at the submarine. When a signal of frequencyf is detected at transducer 31 it is fed through filter 73 and coupled to the input switching means for relay 76 having an armature 77. The signal of frequency f will not be permitted to actuate relay 75 because filter 74 will not permit it to be passed thereto. On the other hand, a signal of frequencyf will only be passed to relay 75 by way of filter 74 and the armature 78 thereof will be closed in response to such a signal. When the signal of frequencyf reaches relay 75 a positive voltage is applied to the input of gyrocompass 58 and a left turn will be cffectuated by the torpedo. lf a signal of frequency f is detected by transducer 31, a right turn will be effected by the torpedo since a signal of opposite polarity will be applied to gyrocompass 58 by potentiometer 54 than that which was applied from potentiometer 53.

[fit is desired, of course it is to be understood that the torpedo containing apparatus such as shown in FIG. 7 may contain correlation apparatus in order to discrimi- 'nate between spurious signals *which might be generated in the water medium carrying the signals. Such apparatus will result in greater system reliance and improved operability.

There has herein been disclosed a system and method by which a torpedo can be guided to a distant weapon by means of a single communication between the torpedo and the launching vessel. This system provides maximum protection to the launching submarine and does not permit the enemy vessel to take effective evasive tactics because the signal command is given at a time when the torpedo is able to home onto any escape area in which the enemy submarine might be able to reach after the command is given.

It will be understood that various changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in appended claims.

What is claimed is:

I. A method of destroying a target with a homing torpedo comprising the steps of detecting the target range and bearing in a passive manner, computing the expected target position after a predetermined period of time from the initially detected range and bearing, adjusting a torpedo turning means mounted on the torpedo prior to the launching of the torpedo to cause the torpedo to turn through a fixed angle upon actuation by a signal, launching the torpedo toward the expected target position, rotating a disc having indicia at a position remote from the torpedo, rotating a disc on the torpedo in synchronism with the indicia bearing disc, generating an acoustic signal only when the torpedo is approximately a predetermined distance from the target to actuate the turning means, the direction of the torpedo turn being controlled by the position of the disc on the torpedo, generating the acoustic signal exactly at a time indicated by the indicia bearing disc corresponding to the direction of the target relative to the torpedo, whereby the torpedo is directed to an area where it can home on the target.

2. The method of claim 1 wherein the fixed angle is substantially 90 and the predetermined distance is the minimum distance between the torpedo and the target.

3. The method of claim 1 wherein the generated signal is a single pulse acoustic signal.

4. The method of destroying a target comprising the steps of detecting the range, bearing, and velocity of the target, computing the expected position of the target at a predetermined time, adjusting a torpedo turning means mounted on the torpedo prior to the launching of the torpedo to cause the torpedo to turn through an angle of 90 upon actuation by a signal. sending a homing torpedo from a launching position along a predetermined path toward the expected target position, and generating a signal at the launching position to actuate the turning means and thereby turn said torpedo only once through an angle of substantially 90 in a direction toward the target when the distance between the target and the torpedo is substantially a minimum whereby the torpedo is directed to an area where it can home on the target.

5. A torpedo control system comprising means carried by the torpedo for detecting a signal generated at a point remote from the torpedo, means contained within the torpedo for turning the torpedo through an angle determined prior to launching of the torpedo only when the remotely generated signal is received and means coupled to said detecting means and to said turning means for controlling the direction of the torpedo turn in response to the received signal, wherein said means for turning comprises a pair of torpedo rudders, a gear train coupled to said rudders, a motor having the shaft thereof coupled to said gears, a gyrocompass coupled to said motor, and a pair of variable voltage sources of opposite polarity coupled to said gyrocompass.

6. The apparatus of claim 5 wherein said control means comprises a constant speed motor for driving a disc having insulated and conducting portions, and a switch having an input coupled to said detecting means and a plurality of outputs, two of said outputs being normally open switching elements, each successively coupled between one of said voltage sources and one of the disc portions, and another output being a normally closed switching element coupled to the constant speed motor power supply.

7. The apparatus of claim 5 wherein said control means comprises a pair of filters coupled to said detecting means for passing different frequency signal bands and a pair of normally open switches controlled by said detecting means, each coupled to a respective filter and to a respective voltage source.

8. A torpedo control system comprising means carried by the torpedo for detecting a signal generated at a point remote from the torpedo, means contained within the torpedo for turning the torpedo through an angle determined prior to launching of the torpedo only when the remotely generated signal is received and means coupled to said detecting means and to said turning means for controlling the direction of the torpedo turn in response to the received signal, wherein said control means comprises a constant speed motor for driving a disc having a insulated ,and a conducting portion, and a switch having an input coupled to said detecting means and a plurality of outputs, two of said outputs being normally open switching elements, each successively coupled between one of the disc portions and said turning means, and another output being a normally closed switching element coupled to the constant speed r notor power supply.

9. A torpedo control system comprising means carried by the torpedo for detecting a signal generated at a point remote from ,the torpedo, means contained within the torpedo for turning the torpedo through an angle determined prior to launching of the torpedo only when the remotely generated signal is received and means coupled to said detecting means and to said signal bands and a pair of normally open switches controlled by said detecting means, each coupled to a respective filter and to said turning means l l l 

1. A method of destroying a target with a homing torpedo comprising the steps of detecting the target range and bearing in a passive manner, computing the expected target position after a predetermined period of time from the initially detected range and bearing, adjusting a torpedo turning means mounted on the torpedo prior to the launching of the torpedo to cause the torpedo to turn through a fixed angle upon actuation by a signal, launching the torpedo toward the expected target position, rotating a disc having indicia at a position remote from the torpedo, rotating a disc on the torpedo in synchronism with the indicia bearing disc, generating an acoustic signal only when the torpedo is approximately a predetermined distance from the target to actuate the turning means, the direction of the torpedo turn being controlled by the position of the disc on the torpedo, generating the acoustic signal exactly at a time indicated by the indicia bearing disc corresponding to the direction of the target relative to the torpedo, whereby the torpedo is directed to an area where it can home on the target.
 2. The method of claim 1 wherein the fixed angle is substantially 90* and the predetermined distance is the minimum distance between the torpedo and the target.
 3. The method of claim 1 wherein the generated signal is a single pulse acoustic signal.
 4. The method of destroying a target comprising the steps of detecting the range, bearing, and velocity of the target, computing the expected position of the target at a predetermined time, adjusting a torpedo turning means mounted on the torpedo prior to the launching of the torpedo to cause the torpedo to turn through an angle of 90* upon actuation by a signal, sending a homing torpedo from a launching position along a predetermined path toward the expected target position, and generating a signal at the launching position to actuate the turning means and thereby turn said torpedo only once through an angle of substantially 90* in a direction toward the target when the distance between the target and the torpedo is substantially a minimum whereby the torpedo is directed to an area where it can home on the target.
 5. A torpedo control system comprising means carried by the torpedo for detecting a signal generated at a point remote from the torpedo, means contained within the torpedo for turning the torpedo through an angle determined prior to launching of the torpedo only when the remotely generated signal is received and means coupled to said detecting means and to said turning means for controlling the direction of the torpedo turn in response to the received signal, wherein said means for turning comprises a pair of torpedo rudders, a gear train coupled to said rudders, a motor having the shaft thereof coupled to said gears, a gyrocompass coupled to said motor, and a pair of variable voltage sources of opposite polarity coupled to said gyrocompass.
 6. The apparatus of claim 5 wherein said control means comprises a constant speed motor for driving a disc having insulated and conducting portions, and a switch having an input coupled to said detecting means and a plurality of outputs, two of said outputs being normally open switching elements, each successively coupled between one of said voltage sources and one of the disc portions, and another output being a normally closed switchinG element coupled to the constant speed motor power supply.
 7. The apparatus of claim 5 wherein said control means comprises a pair of filters coupled to said detecting means for passing different frequency signal bands and a pair of normally open switches controlled by said detecting means, each coupled to a respective filter and to a respective voltage source.
 8. A torpedo control system comprising means carried by the torpedo for detecting a signal generated at a point remote from the torpedo, means contained within the torpedo for turning the torpedo through an angle determined prior to launching of the torpedo only when the remotely generated signal is received and means coupled to said detecting means and to said turning means for controlling the direction of the torpedo turn in response to the received signal, wherein said control means comprises a constant speed motor for driving a disc having a insulated and a conducting portion, and a switch having an input coupled to said detecting means and a plurality of outputs, two of said outputs being normally open switching elements, each successively coupled between one of the disc portions and said turning means, and another output being a normally closed switching element coupled to the constant speed motor power supply.
 9. A torpedo control system comprising means carried by the torpedo for detecting a signal generated at a point remote from the torpedo, means contained within the torpedo for turning the torpedo through an angle determined prior to launching of the torpedo only when the remotely generated signal is received and means coupled to said detecting means and to said turning means for controlling the direction of the torpedo turn in response to the received signal, wherein said control means comprises a pair of filters coupled to said detecting means for passing different frequency signal bands, and a pair of normally open switches controlled by said detecting means, each coupled to a respective filter and to said turning means. 